The present invention relates to a spectroscope apparatus, and more particularly to a two-dimensional imaging monochrometer apparatus which can continuously form a plurality of two-dimensional images of a to-be-measured body due to different light components each having a desired spectral width.
Further, the present invention relates to a method of and an apparatus for controlling reaction which is accompanied by light emission due to reaction, discharge or others, and more particularly to a method of and an apparatus for controlling a reactor or instrument containing a light emitting body, on the basis of those images of the light emitting body which are formed by a two-dimensional spectroscope apparatus and are formed of different wavelength component emitted from the light emitting body.
In a conventional apparatus for monitoring or controlling a reactor or instrument containing a substance which emits light on the basis of reaction, discharge and others, a monitor window is provided at the wall of the reactor or instrument, and the inside of the reactor or instrument is observed through the window to control variable quantities contributing to the chemical change of the substance.
For example, in a thermal power station or the like, the state of combustion flames is observed by an industrial television camera through the monitor window, and it is judged on the basis of the above observation and analytical values of exhaust gas whether the state of combustion flames is appropriate or not, to control the quantities of air and fuel so as to obtain optimum flames. Further, an image indicating the brightness distribution in combustion flames is formed on the basis of the observation on combustion flames by the industrial television camera, to be used for monitoring and controlling the combustion flames. For example, a method of monitoring and controlling combustion flames on the basis of the output of a photodetector which receives light from the combustion flames, is disclosed in a Japanese Patent Application JP-A-No. 56-151,814, and a control method using a video signal from a television camera is disclosed in a Japanese Patent Application JP-A-No. 54-94,125. In these methods, however, the output of an industrial television camera due to all the wavelength components emitted from a light emitting substance (namely, light emitting body) is used for monitoring and controlling the light emitting body. That is, the methods fail to use only a desired wavelength component emitted from the light emitting body, for the purpose of monitoring and controlling the above body. In general, the emission spectrum of the light emitting body is based upon active atoms, molecules and radicals which are contained in this body. The information due to each of wavelength components from the light emitting body makes it possible to estimate the state of the body on the level of atom, molecule and radical, and is indispensable for accurate monitoring and control operations.
A method of monitoring or controlling a flame on the basis of the information due to each of wavelength components emitted from the flame, is disclosed in, for example, a Japanese Patent Application JP-A-No. 53-107,890. In this method, the state of a flame is monitored and controlled on the basis of the correlation between the intensities of OH-radical line, C.sub.2 -radical line and CH-radical line appearing on the emission spectrum of the flame and analytical values of exhaust gas. In the method, however, the intensity of each wavelength component emitted from a point in the flame or the sum of intensities of all wavelength components emitted from the whole region of the flame is used, and thus it is impossible to obtain an image which indicates the distribution of each wavelength component in the flame. Generally speaking, in the reaction generating a light emitting body which always moves, such as a flame, detailed information on the distribution of each wavelength component, that is, the distribution of each chemical species in the flame, teaches the progress of the reaction and the fine structure of the flame, and suggests a position where nitrogen oxide and soot are generated.
Accordingly, a method is required which has not only an advantage of spectrochemical analysis (that is, an advantage that information on each of chemical species in the flame is obtained), but also are advantage of an industrial television camera (that is, an advantage that an image of the flame is formed). There has been known a method, in which an interference filter capable of transmitting only a desired wavelength is provided in front of an industrial television camera. According to this method, an image of a light emitting body can be formed of a desired one of wavelength components emitted from the body. In this method, however, it is necessary to prepare a plurality of interference filters, and it is impossible to change the measuring wavelength continuously, since replacement of interference filter is required for changing the measuring wavelength. Further, an interference filter attenuates light in a great degree, and thus makes it impossible to obtain a clear image by the industrial television camera.
Further, reaction accompanied by light emission occurs in the following apparatuses and methods, that is, a photochemical vapor deposition apparatus (disclosed in a Japanese Patent Application JP-A-No. 56-42,331), a vapor epitaxial growth apparatus (disclosed in a Japanese Patent Application JP-A-No. 58-33,826), a semiconductor fabricating method (disclosed in a Japanese Patent Application JP-A-No. 59-61,123), a method of forming a nitride film (disclosed in a Japanese Patent Application JP-A-No. 56-38,464) and a chemical vapor deposition apparatus (disclosed in a Japanese Patent Application JP-A-No. 59-16,966). In any one of these patent applications, the distribution of each of chemical components of a light emitting body in the body is not measured, and it is not disclosed to monitor and control the light emitting body on the basis of information on the above distribution.
In the simplest conventional method for forming a plurality of images of an object to be measured, of different light components each having a spectral width, optical filters are used, each of which transmits only a light component having a desired spectral width and absorbs or reflects other light components. For example, in a case where a photograph is taken by an ordinary camera in a state that strong ultraviolet rays are present, when an ordinary film is used, blurs in color tone are produced. Accordingly, an ultraviolet cut filter is used, to form an image only of visible light.
Further, in order to thoroughly investigate discharge and combustion phenomena, it is necessary to observe the spatial intensity distribution of a wavelength component peculiar to each of unstable chemical species existing in a discharge plasma or flame such as radicals and active molecules. In this case, only specified wavelength components are measured, and thus optical filters each capable of transmitting one of the specified wavelength components are used. For example, the measurement of unstable chemical species contained in a flame is described in an article (Applied Physics B. Vol. 29, 1982, pages 93 to 97). It is shown in FIG. 1 of this article to use a filter for light from the OH-radical and another filter for light from the C.sub.2 -radical. However, in a method of forming an image due to light within a specified wavelength range by using a filter, it is required to change the specified wavelength range by the replacement of filter, and hence it is impossible to change a measuring wavelength continuously. Further, a filter attenuates light in a great degree. In the above article, no regard is paid to such problems.
An optical apparatus for forming a plurality of images of an object due to different wavelength components continuously by using a spectroscope, is described on page 20 of the abstracts of the spring meeting of the Spectroscopical Society of Japan held in May, 1985. In this optical apparatus, the measuring wavelength can be continuously varied by rotating a grating included in the spectroscope. Further, in the spectroscope, light reflection is repeated, and no optical filter is used. Thus, light is scarcely attenuated in the spectroscope. In this optical apparatus, however, as is apparent from the description that, since a background having a continuous spectrum is present, a wavelength component which exists in the vicinity of a band head and is not affected by a band spectrum, is used, and an image formed of the wavelength component is corrected by software, there arises the following problem. That is, in a case where light emitted from an object to be measured has a continuous spectrum, the measurement is restricted as above. Further, it is required to correct an image by software, and thus the optical apparatus is complicated in structure.
As mentioned above, in a method of taking desired wavelength components out of light emitted from an object to be measured, by using filters to form a plurality of images of the to-be-measured object, there arise problems that it is impossible to change the taken-out wavelength component continuously, since the wavelength component is changed by the replacement of filter, and that each filter absorbs light, and thus the intensity of the taken-out wavelength component is greatly reduced. Further, in a method of taking out desired wavelength components by using a spectroscope, the taken-out wavelength can be continuously varied, but there arise optical problems that when light incident on the spectroscope has a continuous spectrum within a wavelength range, measurement is restricted as mentioned above or a desired image cannot be formed.